This invention relates to a process for recovering phosphate ester type hydraulic fluids from industrial waste liquids and, more particularly, to such a process adapted for use with industrial waste waters also containing polychlorinated biphenyls, organic solvents, and other materials commonly used in connection with die casting operations.
Die casting machines commonly employ relatively expensive fire-resistant hydraulic fluids. Pydraul 50E, a mixture of phosphate esters marketed by Monsanto, is an example of such a hydraulic fluid. Die casting machines typically leak to some degree and the hydraulic fluid along with other materials such as organic solvents, die sprays, die lubricants, die release agents, sawdust, dirt, wash water, etc., end up in floor drains. Because of the high cost, it is highly desirable to recover the hydraulic fluid from the waste water collected in the drain system for reuse.
In the past, fluids including polychlorinated biphenyls (PCB) have been used in die casting machines. Some die casting machines still contain some of these fluids. Present government regulations impose stringent disposal requirements on materials containing PCB. Any leakage of these older fluids into floor drainage systems could result in the waste water having a PCB content above an acceptable level.